This invention relates to transfer mechanisms and, more particularly, this invention relates to an improved conveyor drive unit for use in a transfer mechanism for transporting articles or containers.
Article transfer or conveying systems used in industry have often utilized chain-type conveyors disposed alongside each other and have used a "dead plate" between conveyor stations. However, articles tend to remain on the dead plate if no articles immediately follow the moving articles to push them along. Also, there is nothing to prevent unstable articles from falling over when pushed onto or off of the dead plate. Moreover, the friction inherent between the chain and certain types of the moving articles which it supports could cause backing up of the articles. This problem was recognized and a solution has been provided with the use of rollers as means for supporting and conveying the articles.
With the use of rollers, there is much less contact area between the conveyor surface and the articles, thereby improving the control of the articles being transported. Moreover, as with U.S. Pat. No. 4,313,536, separate drive systems can be implemented at various portions of a roller-type conveyor system which further increases flexibility in the movement of the articles and relieves pressure due to article accumulation.
U.S. Pat. No. 4,313,536 describes separate drive systems in order to obtain flexibility in controlling the movement of articles. In this drive system, a drive shaft with a gear and a system of pinion gears driven thereby are openably mounted on thin mounting plates. The pinion gears drive rigid shafts which, in turn, are connected to the rollers via flexible shafts. The drive shaft is enclosed within bushings located between the thin mounting plates. Thus, heat generated in the rotating elements, especially the drive shaft and the sprocket wheel, of the drive unit of the above-cited patent cannot be dissipated by the mounting plates. The heat is, therefore, retained in the unit, possibly leading to the annealing or weakening of the affected elements.
In addition, the sprocket wheel used on the device of U.S. Pat. No. 4,313,536 requires multiple "hang loads" on the drive shaft, including the bearing and washers abutting the sprocket wheel, as well as the spring and washers abutting the end bolt for making up the clutch-type mechanism for engaging the sprocket wheel to the drive shaft. Thus, a significant vertical load is applied to the drive shaft thereby contributing to the bending stress on the drive shaft. Further, the sprocket wheel is of a design requiring an increased pressure from the chain to drive the sprocket wheel further contributing to the undesirable stresses, including bending and torsion stresses, exerted on the drive shaft. Still further, sets of rollers operated by a single chain can jam when debris or an article is caught between a set of rollers operated by a drive unit since the sprocket wheel cannot stop the drive unit under such conditions.
Accordingly, there is a need for an efficient, economical, simply constructed and easily installed improved conveyor drive unit for providing a much reduced load applied on the drive shaft.